The University of Cincinnati Division of Toxicology is uniquely qualified to serve as an ACTG Pharmacology Core Laboratory. Through the Division's research and development programs, its commitment in the battle against HIV disease has been documented through numerous publications and abstracts, and by the initiation of ACTG 161, a pharmacokinetic study of total phosphorylated zidovudine in HIV-infected patients. The Division of Toxicology can offer a full range of State- of-the-Art equipment and experience, and currently represents the leading edge in the development of assays for active intracellular metabolites of nucleoside analogs in patients, specifically zidovudine. Currently, the University of Cincinnati Division of Toxicology is the only laboratory capable of performing assays for ACTG 161, and any similar future studies. Because the Division is hospital based, procedures and facilities for sample receipt, handling, storage, and billing are already in place. Furthermore, as a clinical laboratory, adherence to strict regulated standards of quality assurance and control are required. The Division of Toxicology has a strong history of cooperation with the University of Cincinnati ACTU, and hopes to continue the same level of cooperation in the future.